Apparatus and method for feeding back data receiving status

ABSTRACT

An apparatus and a method for feeding back data receiving status, applied to a system, are provided. The method includes sequencing, by a User Equipment (UE), downlink subframes for transmitting data with respect to each Component Carrier (CC), generating receiving status feedback information for the first X downlink subframes with respect to each CC according to the result of the sequencing, where X≦M, wherein M is the number of downlink subframes on each CC, and transmitting the receiving status feedback information generated with respect to each CC to a base station. Accordingly, the UE will not misinterpret the receiving status for the downlink subframes due to inconsistencies with the base station between transmitting and receiving feedback. This affects the Hybrid Automatic Repeat Request (HARQ) transmission, saves the uplink overheads occupied by the receiving status feedback information, and increases the uplink coverage area.

PRIORITY

This application claims the benefit under 35 U.S.C. §119(a) of a Chinesepatent application filed on Apr. 30, 2010 in the Chinese IntellectualProperty Office and assigned Serial No. 201010168684.8, a Chinese patentapplication filed on Oct. 27, 2010 in the Chinese Intellectual PropertyOffice and assigned Serial No. 201010527462.0, a Chinese patentapplication filed on Nov. 16, 2010 in the Chinese Intellectual PropertyOffice and assigned Serial No. 201010574732.3, and a Chinese patentapplication filed on Dec. 1, 2010 in the Chinese Intellectual PropertyOffice and assigned Serial No. 201010589610.1 the entire disclosures ofeach of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of radio communicationtechnologies. More particularly, the present invention relates to anapparatus and a method for feeding back data receiving status.

2. Description of the Related Art

A Long Term Evolution (LTE) system transmits data based on HybridAutomatic Repeat Request (HARQ), i.e., a data receiver will sendreceiving status feedback information of Acknowledgement (ACK) orNon-Acknowledgement (NACK) according to the corresponding data receivingstatus. Scheduling information for dynamic downlink data transmission istransmitted through a Physical Downlink Control Channel (PDCCH), whereasexcept for Semi-Persistent Scheduling (SPS), initial transmissionscheduling information for downlink data does not need to be transmittedthrough the PDCCH, and only at the time of retransmission of thedownlink data, the scheduling information needs to be transmittedthrough the PDCCH.

For an LTE Time Division Duplexing (TDD) system, when the number ofdownlink subframes is larger than that of uplink subframes, receivingstatus feedback information for the data of multiple downlink subframesneeds to be transmitted collectively in the same uplink subframe. One ofthe methods for the feeding back is to perform an “AND” operation on thereceiving status feedback information for the downlink subframes thattransmit data, so as to obtain receiving status feedback information ofone bit for each code word. Because the downlink data transmission isscheduled dynamically through a PDCCH, and User Equipment (UE) may notbe able to receive a PDCCH transmitted from a base station, there may beinconsistencies between the receiver and transmitter in the method ofperforming an “AND” operation according to code word. To address thisproblem, a Downlink Assignment Index (DAI) is used in the LTE TDD systemto indicate the serial number of the current downlink subframe in theradio frame that transmits the PDCCH, so that the UE can detect whethera PDCCH in the downlink subframes has been lost. For a radio frame with4 downlink subframes, the value of the DAI may be 1, 2, 3 and 4.

There is, however, a problem with the above method, i.e., a case inwhich the last several PDCCHs are lost cannot be detected. In the LTETDD, therefore, it is specified that the UE needs to feed back receivingstatus feedback information on a receiving status feeding-back channelcorresponding to the last one downlink subframe that receives a PDCCH,so that the base station can get aware of whether the UE has lost thePDCCHs of the last several downlink subframes from the channel on whichthe UE feeds back the receiving status feedback information.

In a Long Term Evolution-Advanced (LTE-A) system, a Carrier Aggregation(CA) technology has been used to support a higher transmission rate, inwhich two or more Component Carriers (CC) are aggregated to obtain alarger working bandwidth. For example, to support a bandwidth of 100MHz, 5 CCs of 20 MHz may be aggregated. Based on CA, the base stationtransmits downlink data to the UE on two or more CCs. Correspondingly,the UE also needs to support the receiving status feedback informationfor the downlink data received from the two or more CCs.

According to the current results of discussions on LTE-A, at most 4 bitsof ACK/NACK transmission can be supported based on the technology ofchannel selection. In LTE-A Frequency Division Duplexing (FDD), themethod of channel selection actually supports only two CCs and at most 2bits of ACK/NACK information can be fed back on each CC. Taking a 4-bittable as an example, for a Primary CC (PCC) and a Secondary CC (SCC)employing cross-CC scheduling, the two ACK/NCK channels are obtained byscheduling PDCCHs for downlink data transmission. For example, assumingthe minimum CCE index of PDCCH is n, the two ACK/NACK channels may beobtained through mapping by using an LTE method from CCE indexes n andn+1. For a SCC not employing cross-CC scheduling, the two ACK/NACKchannels are configured by the higher layer, and the flexibility inassignment may be increased through an ACK/NACK Resource Indicator(ARI). According to the current results of discussions, a 4-bit mappingtable as shown in FIG. 3 is employed in an FDD system. Here, ACK/NACKchannels 1 and 2 correspond to the two ACK/NACK bits of a PCCsequentially and ACK/NACK channels 3 and 4 correspond to the twoACK/NACK bits of a SCC sequentially. In the table of FIG. 3, the featurethat the two ACK/NACK channels always are present at the same time on orabsent at the same time from the same CC is utilized to optimize theperformance. Another 4-bit mapping table is as shown in FIG. 12. Here,only when some ACK/NACK information is ACK, the ACK/NACK channelcorresponding thereto is selected for transmission. The only exceptionis that to take full advantage of the feedback capabilities of M (M isequal to 2, 3 or 4) ACK/NACK channels, when the first piece of ACK/NACKinformation is NACK and the remaining pieces of ACK/NACK information areall NACK or Discontinuous Reception (DRX), a Quadrature Phase-ShiftKeying (QPSK) constellation point of the first ACK/NACK channel may beused for the indication. The method as illustrated in FIG. 12 may beapplied to the scenario in which the 4 ACK/NACK bits and thecorresponding ACK/NACK channels are all independent of one another.

In the tables, N denotes NACK, A denotes ACK, D denotes DRX and thesymbol “/” denotes “or”.

For an LTE-A TDD system, in a case of supporting CA, the UE needs tofeed back significantly more bits of receiving status feedbackinformation than in single carrier transmission. For example, when aradio frame has 4 downlink subframes for transmitting data and 5 CCs,assuming Multiple Input Multiple Output (MIMO) data transmission isconfigured for the UE, 40 bits of receiving status feedback informationneed to be fed back. Apparently, if the method of feeding back receivingstatus feedback information for single carrier is also used, many uplinkoverheads will be occupied and the uplink coverage area will be reduced.Moreover, all the uplink control channels currently supported in an LTEsystem cannot support so large an amount of receiving status feedbackinformation. If it needs to support 40 bits of feedback, the structureof feeding-back channels needs to be redefined, which significantlyincreases the complexity of standardization.

Therefore, a need exists for an apparatus and a method for feeding backdata receiving status, so as to reduce the uplink overheads occupied bythe receiving status feedback information and increase the uplinkcoverage area.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide an apparatus and a method for feeding back datareceiving status, so as to reduce the uplink overheads occupied by thereceiving status feedback information and increase the uplink coveragearea.

In accordance with an aspect of the present invention, a method forfeeding back data receiving status, applied to a system is provided. Themethod includes sequencing, by an User Equipment (UE), downlinksubframes for transmitting data with respect to each Component Carrier(CC), generating receiving status feedback information for the first Xdownlink subframes with respect to each CC according to the result ofthe sequencing, where X≦M, wherein M is the number of downlink subframeson each CC, and transmitting the receiving status feedback informationgenerated with respect to each CC to a base station.

As can be seen from the above technical description, the UE sequencesdownlink subframes for transmitting data with respect to each CC,generates receiving status feedback information for the first X downlinksubframes according to the result of the sequencing, and transmits thereceiving status feedback information for each CC to the base station.Because the UE reports the receiving status for only X downlinksubframes, the base station may perform a Hybrid Automatic RepeatRequest (HARQ) processing on the first X downlink subframes. For thelast downlink subframes, the base station may perform a processing byassuming that the UE does not receive the Physical Downlink ControlChannels (PDCCHs). Therefore, the base station can reach an agreementwith the UE on the receiving status of the UE, ensuring that the UE willnot misinterpret the receiving status for the downlink subframes due toinconsistencies with the base station between transmitting and receivingfeedback so that the HARQ transmission is affected. Moreover, anexemplary embodiment of the present invention employs a method offeeding back the receiving status feedback information for only thefirst X downlink subframes, which, in the Carrier Aggregation (CA)technology, saves the uplink overheads occupied by the receiving statusfeedback information and increases the uplink coverage area.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a flowchart illustrating a method for feeding back datareceiving status according to an exemplary embodiment of the presentinvention;

FIG. 2 illustrates a downlink subframe transmission status according toan exemplary embodiment of the present invention;

FIG. 3 illustrates a 4-bit mapping table employed in a Long TermEvolution-Advanced (LTE-A) Frequency Division Duplexing (FDD) systemaccording to an exemplary embodiment of the present invention;

FIG. 4 illustrates bundled feedback status when M=2 according to anexemplary embodiment of the present invention;

FIG. 5 illustrates bundled feedback status when M=3 according to anexemplary embodiment of the present invention;

FIG. 6 illustrates bundled feedback status when M=4 according to anexemplary embodiment of the present invention;

FIG. 7 illustrates a mapping relationship from feedback status to 2-bitAcknowledgement/Non-Acknowledgement (ACK/NACK) in an FDD table accordingto an exemplary embodiment of the present invention;

FIG. 8 illustrates processing 5 types of feedback information into 4types of status to be fed back according to an exemplary embodiment ofthe present invention;

FIG. 9 illustrates processing 5 types of feedback information into 4types of status to be fed back according to an exemplary embodiment ofthe present invention;

FIG. 10 illustrates processing 5 types of feedback information into 4types of status to be fed back according to an exemplary embodiment ofthe present invention;

FIG. 11 illustrates processing 5 types of feedback information into 4types of status to be fed back according to an exemplary embodiment ofthe present invention;

FIG. 12 illustrates a 4-bit mapping table according to an exemplaryembodiment of the present invention;

FIG. 13 illustrates a mapping relationship from feedback status to 2-bitACK/NACK according to an exemplary embodiment of the present invention;and

FIG. 14 is a block diagram illustrating an apparatus for feeding backdata receiving status according to an exemplary embodiment of thepresent invention.

Throughout the drawings, like reference numerals will be understood torefer to like parts, components and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to skill in theart, may occur in amounts that do not preclude the effect thecharacteristic was intended to provide.

Exemplary embodiments of the present invention provide an apparatus anda method for feeding back data receiving status, so as to reduce theuplink overheads occupied by the receiving status feedback informationand increase the uplink coverage area.

FIGS. 1 through 14, discussed below, and the various exemplaryembodiments used to describe the principles of the present disclosure inthis patent document are by way of illustration only and should not beconstrued in any way that would limit the scope of the disclosure. Thoseskilled in the art will understand that the principles of the presentdisclosure may be implemented in any suitably arranged communicationssystem. The terms used to describe various embodiments are exemplary. Itshould be understood that these are provided to merely aid theunderstanding of the description, and that their use and definitions inno way limit the scope of the invention. Terms first, second, and thelike are used to differentiate between objects having the sameterminology and are in no way intended to represent a chronologicalorder, unless where explicitly state otherwise. A set is defined as anon-empty set including at least one element.

FIG. 1 is a flowchart illustrating a method for feeding back datareceiving status according to an exemplary embodiment of the presentinvention.

Referring to FIG. 1, a User Equipment (UE) sequences downlink subframesfor transmitting data for the UE with respect to each Component Carrier(CC) in step 101. More particularly, sequencing priorities may be setfrom higher to lower for downlink subframes transmitting Semi PersistentScheduling (SPS) service data and downlink subframes transmittingdynamic data.

If there are multiple downlink subframes transmitting SPS service data,they may be sequenced by subframe indexes occupied by the downlinksubframes transmitting SPS service data. If there are multiple downlinksubframes transmitting dynamic data, they may be sequenced in anascending order of Downlink Assignment Indexes (DAIs).

If there is no downlink subframe transmitting SPS service data, downlinksubframes transmitting dynamic data may be sequenced directly in anascending order of DAIs.

In Carrier Aggregation (CA), there may be some CCs transmitting data notfor the UE, or the UE may have not received data from some CCs. For suchCCs, receiving status feedback information of Discontinuous Reception(DRX) is generated directly. That is to say, the CCs from which the UEhas not received data will not be involved in steps 102 and 103,according to an exemplary embodiment of the present invention.

In step 102, receiving status feedback information for the first Xdownlink subframes may be generated with respect to each CC according tothe order of the downlink subframes for transmitting data, where X≦M, Mbeing the number of downlink subframes on a CC. In this step, receivingstatus feedback information is generated with respect to each CCaccording to the sequencing in step 101.

According to an exemplary embodiment of the present invention, only thereceiving status feedback information for the first X downlink subframesis fed back with respect to each CC. The receiving status feedbackinformation as fed back may include all Acknowledgement (ACK) for thefirst X downlink subframes or all Non-Acknowledgement (NACK) for thefirst X downlink subframes. Alternatively, both ACK and NACK may beincluded, i.e., ACK for some of the first X downlink subframes and NACKfor others, DRX for some of the first X downlink subframes, or others.No feedback will be made for the last M−X downlink subframes. Moreparticularly, X may not have a fixed value, and may take differentvalues depending on different receiving status feedback information forthe downlink subframes sequenced according to step 101.

Upon receiving the receiving status feedback information on the CC, thebase station performs a Hybrid Automatic Repeat Request (HARQ)processing on the downlink data of the first X downlink subframesaccording to the corresponding receiving status feedback information.For the downlink data of the last M−X downlink subframes, the basestation has to perform a processing by assuming that the UE does notreceive the Physical Downlink Control Channels (PDCCHs) that schedulesuch data.

The UE may first perform spatial bundling on the receiving statusfeedback information for two Code Words (CWs) in each downlink subframe.That is to say, in a case of Multiple Input Multiple Output (MIMO)transmission, an “AND” operation is performed on the receiving statusfeedback information for the two CWs to obtain a piece of bundledreceiving status feedback information. When no MIMO transmission isapplied, one piece of receiving status feedback information is obtaineddirectly. Afterwards, the receiving status feedback information for onlythe first X downlink subframes is fed back and no feedback is made forthe last M−X downlink subframes.

If more accurate receiving status needs to be fed back, the spatialbundling may not be performed. That is, in the case of MIMO datatransmission, receiving status feedback information for two CWs is fedback with respect to each subframe of the first X downlink subframes. Inthis case, two exemplary implementations of generating receiving statusfeedback information may be used.

In a first exemplary implementation, receiving status feedbackinformation for the first X1 downlink subframes is fed back with respectto a CW with an index of 0 and receiving status feedback information forthe first X2 downlink subframes is fed back with respect to a CW with anindex of 1, where X1≦M and X2≦M. X1 and X2 may or may not be equal toeach other. That is to say, receiving status feedback information forthe first several downlink subframes is fed back with respect to eachCW.

With respect to the CW with an index of 0, the generated receivingstatus feedback information may be all ACK for the first X1 downlinksubframes or all NACK for the first X1 downlink subframes.Alternatively, both ACK and NACK may be included, i.e., ACK for some ofthe first X1 downlink subframes and NACK for others, DRX for some of thefirst X1 downlink subframes, or others. Similarly, with respect to theCW with an index of 1, the generated receiving status feedbackinformation may be all ACK for the first X2 downlink subframes or allNACK for the first X2 downlink subframes. Alternatively, both ACK andNACK may be included, i.e., ACK for some of the first X2 downlinksubframes and NACK for others, DRX for some of the first X2 downlinksubframes, or others.

Upon receiving the receiving status feedback information on the CC thatis fed back respectively with respect to the two CWs, the base stationperforms a HARQ processing on the CW with an index of 0 in the first X1downlink subframes according to the corresponding receiving statusfeedback information. For the CW with an index of 0 in other downlinksubframes, the base station performs a processing by assuming that theUE does not receive the PDCCHs that schedule such downlink subframes.The base station performs a HARQ processing on the CW with an index of 1in the first X2 downlink subframes according to the correspondingreceiving status feedback information. For the CW with an index of 1 inother downlink subframes, the base station performs a processing byassuming that the UE does not receive the PDCCHs that schedule suchdownlink subframes.

Taking an example for the first method, assume MIMO data transmission isapplied to a CC and no spatial bundling is performed, but receivingstatus feedback information for each CW is fed back. If M is equal to 3,5 types of receiving status feedback information may be generated foreach CW. For example, 1) all ACK for receiving status feedbackinformation for the first 3 downlink subframes, 2) all ACK for receivingstatus feedback information for the first 2 downlink subframes, 3) allACK for receiving status feedback information for the first downlinksubframe, 4) NACK and ACK for receiving status feedback information forthe first 2 downlink subframes, and 5) NACK or DRX for receiving statusfeedback information for the first downlink subframe. Therefore, 5×5=25types of information in total need to be fed back with respect to thetwo CWs of each CC.

In a second exemplary implementation, receiving status feedbackinformation for two CWs is fed back respectively with respect to eachsubframe of the first X downlink subframes.

In this case, the generated receiving status feedback information may beall ACK for the two CWs of the first X downlink subframes or all NACKfor the two CWs of the first X downlink subframes. Alternatively, bothACK and NACK may be included, i.e., ACK for the two CWs of some of thefirst X downlink subframes and NACK for the two CWs of others, DRX forthe two CWs of some of the first X downlink subframes, or others.

Upon receiving the receiving status feedback information on the CC forthe first X downlink subframes, the base station performs a HARQprocessing on the two CWs in the first X downlink subframes according tothe corresponding receiving status feedback information. For otherdownlink subframes, the base station performs a processing by assumingthat the UE does not receive the PDCCHs that schedule such downlinksubframes.

Taking an example for the second exemplary implementation, MIMO datatransmission may be applied to a CC and no spatial bundling isperformed, but receiving status for the two CWs in the first X downlinksubframes is fed back respectively. If M is equal to 4, there may be 13types of receiving status feedback information. More particularly, 1)all ACK and ACK for feedback information for the two CWs in the first X(i.e., X is equal to 1, 2, 3 or 4) downlink subframes, 2) all ACK andNACK for feedback information for the two CWs in the first X downlinksubframes, 3) all NACK and ACK for feedback information for the two CWsin the first X downlink subframe, 4) NACK and DRX for feedbackinformation for the two CWs in the first downlink subframe, and so on.

In addition, for a CC configured with a MIMO data transmission mode,only one CW may be transmitted in a subframe, i.e., the other CW is notused to transmit data in the subframe. In this case, one of the handlingmethods is to define a fixed value for feedback information for this CWthat does not transmit data, such as ACK, NACK and DRX. Another handlingmethod is to sequence the downlink subframes with respect to each CW instep 101 and to sequence the downlink subframes only with respect to theCW that actually transmits data. These two handling methods are bothcompatible with the aforementioned method and have no influence thereon.

In step 103, the UE transmits the receiving status feedback informationgenerated with respect to each CC to the base station.

In this step, the UE may employ a method of coding the receiving statusfeedback information for the CCs jointly for transmission. Other methodsmay also be employed, e.g., a method based on channel selection, and thelike.

The UE may feed back receiving status feedback information with respectto all the CCs in a cell, may feed back receiving status feedbackinformation with respect to the CCs configured for the UE by the basestation, or may feed back receiving status feedback information withrespect to the active CCs configured for the UE by the base station.

With regard to step 102, examples of receiving status feedbackinformation fed back with respect to the CCs are described below whereinM takes different values. In this case, it is assumed that 5 types ofinformation need to be fed back with respect to a CC.

Assume M is equal to 2. If spatial bundling is applied to receivingstatus feedback information for each downlink subframe, then based onthe sequencing of downlink subframes for transmitting data in an orderbased on service type and DAI, the receiving status feedback informationmay include 1) both ACK for receiving status feedback information forthe first 2 downlink subframes, 2) ACK for receiving status feedbackinformation for the first downlink subframe, 3) NACK and ACKrespectively for receiving status feedback information for the first 2downlink subframes, 4) NACK for receiving status feedback informationfor the first downlink subframe and not ACK for receiving statusfeedback information for the second downlink subframe, if present, and5) DRX for receiving status feedback information for the first downlinksubframe.

Assume M is equal to 3. If spatial bundling is applied to receivingstatus feedback information for each downlink subframe, then based onthe sequencing of downlink subframes for transmitting data in an orderbased on service type and DAI, the receiving status feedback informationmay include 1) all ACK for receiving status feedback information for thefirst 3 downlink subframes, 2) both ACK for receiving status feedbackinformation for the first 2 downlink subframes, 3) ACK for receivingstatus feedback information for the first downlink subframe, 4) NACK andACK respectively for receiving status feedback information for the first2 downlink subframes, 5) NACK for receiving status feedback informationfor the first downlink subframe and not ACK for receiving statusfeedback information for the second downlink subframe, if present, orDRX for receiving status feedback information for the first downlinksubframe.

Assume M is equal to 4. If spatial bundling is applied to receivingstatus feedback information for each downlink subframe, then based onthe sequencing of downlink subframes for transmitting data in an orderbased on service type and DAI, the receiving status feedback informationmay include 1) all ACK for receiving status feedback information for thefirst 4 downlink subframes, 2) all ACK for receiving status feedbackinformation for the first 3 downlink subframes, 3) both ACK forreceiving status feedback information for the first 2 downlinksubframes, 4) ACK for receiving status feedback information for thefirst downlink subframe, and 5) NACK or DRX for receiving statusfeedback information for the first downlink subframe.

An exemplary embodiment of the present invention is not limited to theabove examples of receiving status feedback information and the numberof types of receiving status feedback information generated with respectto each CC is not limited to 5.

In above step 102, assume 4 types of feedback status need to be fed backfor a CC and thus two bits can be used for the indication thereof. Themethods of generating feedback status will be described below withrespect to different values of M.

FIG. 4 illustrates bundled feedback status when M=2 according to anexemplary embodiment of the present invention.

Referring to FIG. 4, assume M is equal to 2. If spatial bundling isapplied to receiving status feedback information for each downlinksubframe, then based on the sequencing of downlink subframes fortransmitting data in an order based on service type and DAI, as shown inFIG. 4, the 4 types of feedback status are defined as 1) both ACK forreceiving status feedback information for the first 2 downlinksubframes, 2) ACK for receiving status feedback information for thefirst downlink subframe and NACK/DRX for receiving status feedbackinformation for the second downlink subframe, 3) NACK and ACKrespectively for receiving status feedback information for the first 2downlink subframes, and 4) except for feedback status 2), NACK/DRX forreceiving status feedback information for the first downlink subframe.

FIG. 5 illustrates bundled feedback status when M=3 according to anexemplary embodiment of the present invention.

Referring to FIG. 5, assume M is equal to 3. If spatial bundling isapplied to receiving status feedback information for each downlinksubframe, then based on the sequencing of downlink subframes fortransmitting data in an order based on service type and DAI, as shown inFIG. 5, the 4 types of feedback status are defined as 1) all ACK forreceiving status feedback information for the first 3 downlinksubframes, 2) both ACK for receiving status feedback information for thefirst 2 downlink subframes and NACK/DRX for receiving status feedbackinformation for the third downlink subframe, 3) ACK for receiving statusfeedback information for the first downlink subframe and NACK/DRX forreceiving status feedback information for the second downlink subframe,and 4) NACK/DRX for receiving status feedback information for the firstdownlink subframe.

FIG. 6 illustrates bundled feedback status when M=4 according to anexemplary embodiment of the present invention.

Referring to FIG. 6, assume M is equal to 4. If spatial bundling isapplied to receiving status feedback information for each downlinksubframe, then based on the sequencing of downlink subframes fortransmitting data in an order based on service type and DAI, 5 types offeedback information may be obtained first a) all ACK for receivingstatus feedback information for the first 4 downlink subframes, b) allACK for receiving status feedback information for the first 3 downlinksubframes and NACK/DRX for receiving status feedback information for thefourth downlink subframe, c) both ACK for receiving status feedbackinformation for the first 2 downlink subframes and NACK/DRX forreceiving status feedback information for the third downlink subframe,d) ACK for receiving status feedback information for the first downlinksubframe and NACK/DRX for receiving status feedback information for thesecond downlink subframe, and e) NACK/DRX for receiving status feedbackinformation for the first downlink subframe. Then the 4 types of statusto be fed back are obtained through multi-to-one mapping of the 5 typesof feedback information. As shown in FIG. 6, for example, the basestation may map feedback information types a) and d) to the same statustype, i.e., feedback status type 3), and map feedback information typesb), c) and e), respectively, to the other 3 types of status, i.e.,feedback status types 1), 2) and 4), so that they can be indicated with2 bits. With such a multi-to-one method, when both feedback informationtypes a) and d) are possible, the base station cannot determine thefeedback information is actually a) or d). A possible solution is toperform a processing taking the number of successive ACKs as 4 when thebase station has actually transmitted data of 4 subframes and to performa processing taking the number of successive ACKs as 1 when the basestation has actually transmitted data of less than 4 subframes.Exemplary embodiments of the present invention will not limit theparticular behavior of the base station.

FIG. 8 illustrates processing 5 types of feedback information into 4types of status to be fed back according to an exemplary embodiment ofthe present invention.

Referring to FIG. 8, where 4 types of feedback status are obtainedthrough multi-to-one mapping of the 5 types of feedback information,i.e., in which two types of feedback information are combined into thesame status type, the base station may in practice process the combinedstatus type in view of the feedback information type with a less numberof successive ACKs, so as to avoid inconsistencies. As shown in FIG. 8,for example, feedback information types a) and b) are combined intofeedback status type 1) and the other three types of feedbackinformation c), d) and e) are mapped respectively to feedback statustypes 2), 3) and 4). The base station handles, in a fixed way, the HARQtransmission of feedback status type 1) according to feedbackinformation type b), i.e., ACK for receiving status feedback informationfor only the first 3 downlink subframes. In this way, even when the UEreceives the data of 4 subframes completely correctly, the base stationwill retransmit the data of the fourth subframe.

FIG. 9 illustrates processing 5 types of feedback information into 4types of status to be fed back according to an exemplary embodiment ofthe present invention.

Referring to FIG. 9, feedback information types d) and e) are combinedinto feedback status type 4) and the other three types of feedbackinformation a), b) and c) are mapped respectively to feedback statustypes 1), 2) and 3). The base station handles, in a fixed way, the HARQtransmission of feedback status type 4) according to feedbackinformation type e), i.e., retransmits all the data. With this method,there are no inconsistencies with the base station between feedbackinformation types, but unnecessary retransmissions may be increased.

In an exemplary embodiment of the present invention, feedback statustype 1) refers to the first type of feedback status, feedback statustype 2) refers to the second type of feedback status, feedback statustype 3) refers to the third type of feedback status, and feedback statustype 4) refers to the fourth type of feedback status.

In an exemplary implementation of processing the 5 types of feedbackinformation into the 4 types of feedback status, one of the feedbackinformation types is divided into two types of sub-status, which arecombined with two other types of feedback information, so as to obtain 4types of feedback status.

FIG. 10 illustrates processing 5 types of feedback information into 4types of status to be fed back according to an exemplary embodiment ofthe present invention.

Referring to FIG. 10, feedback information type b) may be divided intosub-information type b1), i.e., all ACK for receiving status feedbackinformation for the first 3 downlink subframes and DRX for receivingstatus feedback information for the fourth downlink subframe, andsub-information type b2), i.e., all ACK for receiving status feedbackinformation for the first 3 downlink subframes and NACK for receivingstatus feedback information for the fourth downlink subframe. Thensub-information type b1) and feedback information type a) are combinedinto the same feedback status type 1), sub-information type b2) andfeedback information type c) are combined into the same feedback statustype 2), and feedback information types d) and e) are mappedrespectively to feedback status types 3) and 4). A method performed bythe base station is described as follows. When the base station hasactually scheduled the data of 4 subframes, feedback status type 1) mayindicate that all the 4 subframes have been received correctly or thefirst 3 subframes have been received correctly and the PDCCH of thefourth subframe has been lost. As designed for the Long Term Evolution(LTE) system, the probability of losing a PDCCH is very low, which isabout 0.01 and the UE supporting the CA is in a better channel state sothat the probability of receiving PDCCHs correctly is very high. In animplementation, the base station may also increase purposely theprobability of receiving the PDCCH of the fourth subframe, so as toreduce the probability of sub-information type b1). Therefore, the basestation may treat feedback status type 1) as feedback information typea). When the base station has actually scheduled the data of 4subframes, feedback information type a) is impossible. Therefore, thebase station may treat feedback status type 1) as sub-information typeb1). In the case of feedback status type 2), because there may be nogreat difference between the probabilities of feedback information typec) and sub-information type b2), the base station may handle the HARQtransmission according to feedback information type c) in a fixed way.Here, in the case of sub-information type b2) in actual, the basestation may retransmit the data of the third subframe additionally. Anadvantage of this mapping method lies in that when the base stationschedules data of only less than or equal to 3 subframes, there isactually no repeated mapping of feedback information, thereby ensuringan optimized performance.

FIG. 11 illustrates processing 5 types of feedback information into 4types of status to be fed back according to an exemplary embodiment ofthe present invention.

Referring to FIG. 11, feedback information type d) may be divided intosub-information type d1), i.e., ACK for receiving status feedbackinformation for the first downlink subframe and DRX for receiving statusfeedback information for the last 3 downlink subframes, andsub-information type d2), i.e., ACK for receiving status feedbackinformation for the first downlink subframes and not all DRX forreceiving status feedback information for the last 3 downlink subframes.Thereafter, sub-information type d1) and feedback information type a)are combined into the same feedback status type 1), sub-information typed2) and feedback information type e) are combined into the same feedbackstatus type 4), and feedback information types b) and c) are mappedrespectively to feedback status types 2) and 3). A method performed bythe base station is described as follows. When the base station hasactually scheduled the data of 4 subframes, feedback status type 1) mayindicate that all the 4 subframes have been received correctly or the UEhas received the first subframe correctly and that the PDCCHs of thelast 3 subframes have been lost. As designed for the LTE system, theprobability of losing a PDCCH is very low, which is about 0.01 and theprobability of losing the PDCCH of 3 subframes is even lower. Therefore,when the base station receives feedback status type 1), the possibilityin which the information fed back from the UE actually is a) is veryhigh. Therefore, the base station may treat feedback status type 1) asfeedback information type a). When the base station has actuallyscheduled the data of 4 subframes, feedback information type a) isimpossible. Therefore, the base station may treat feedback statustype 1) as sub-information type d1). In the case of feedback status type4), because there may be no great difference between the probabilitiesof feedback information type e) and sub-information type d2), the basestation may handle the HARQ transmission according to feedbackinformation type e) in a fixed way. In this case, because a user of CAusually needs to transmit many data and with this method, feedbacks onthe scenarios in which the data of 4, 3 and 2 subframes, calculated fromthe first subframe, are received correctly are optimized, it is easy toincrease the downlink throughput when the base station actuallytransmits the data of 4 subframes. However, when the base stationschedules data of only less than or equal to 3 subframes, the feedbackinformation is not optimal with this method.

Exemplary embodiments of the present invention may take full advantageof DAI. The DAI may be used not only for sequencing the downlinksubframes for transmitting data, but also for increasing the informationamount of receiving status feedback information.

FIG. 2 illustrates a downlink subframe transmission status according toan exemplary embodiment of the present invention.

Referring to FIG. 2, an example is illustrated in which, when M is equalto 4, the downlink subframe with a DAI of 1 is the third downlinksubframe of the M downlink subframes. In this case, possible feedbackinformation can only be ACK for receiving status feedback informationfor the first two downlink subframes, ACK for receiving status feedbackinformation for the first downlink subframe, or NACK/DRX for receivingstatus feedback information for the first downlink subframe. It is notpossible that receiving status feedback information for the first 4downlink subframes is ACK and receiving status feedback information forthe first 3 downlink subframes is ACK. Accordingly, the method in whichthere are 5 types of receiving status feedback information cannot takefull advantage of the capability of uplink feedback.

According to an exemplary embodiment of the present invention, the formof receiving status feedback information may be determined according tothe position of the downlink subframe with a DAI of 1 in the M downlinksubframes, thereby increasing the information amount of receiving statusfeedback information for each CC without increasing the overheads andfurther improving the performance of downlink transmission.

More particularly, referring back to step 102 of FIG. 1, the UE canobtain a maximum number N of downlink subframes to which the basestation may transmit downlink data, according to the position of thedownlink subframe with a DAI of 1 in the M downlink subframes. In thiscase, the UE may generate receiving status feedback information in sucha way that receiving status feedback information for the data of Ndownlink subframes is transmitted in an uplink subframe.Correspondingly, the base station receives feedback information also insuch a way that receiving status feedback information for the data of Ndownlink subframes is transmitted in an uplink subframe.

The value of N is discussed below. If no SPS service data is included inthe M downlink subframes, the subframe index of the downlink subframewith a DAI of 1 is assumed to be k, where k takes a value of 1 to M.When the UE receives the PDCCH of the downlink subframe with a DAI of 1,the UE may determine that the maximum value of the number of thedownlink subframes to which the base station transmits data is M−k+1.The UE may transmit feedback information in such a way that receivingstatus feedback information for the data of the M−k+1 downlink subframesis transmitted in an uplink subframe. Correspondingly, the base stationreceives feedback information also in such a way that receiving statusfeedback information for the data of the M−k+1 downlink subframes istransmitted in an uplink subframe.

If SPS service data is included in the M downlink subframes, thesubframe index of the downlink subframe with a DAI of 1 is assumed to bek, where k takes a value of 1 to M, and the number of downlink subframesfor transmitting the SPS service data and each with an index less than kis assumed to be M_(SPS). When the UE receives the PDCCH of the downlinksubframe with a DAI of 1, the UE may determine that the maximum value ofthe number of the downlink subframes to which the base station transmitsdata is M−k+1+M_(SPS). The UE may transmit feedback information in sucha way that receiving status feedback information for the data of theM−k+1+M_(SPS) downlink subframes is transmitted in an uplink subframe.Correspondingly, the base station receives feedback information also insuch a way that receiving status feedback information for the data ofthe M−k+1+M_(SPS) downlink subframes is transmitted in an uplinksubframe.

Referring back to FIG. 2, M is assumed to be equal to 4. Because thebase station has actually scheduled and transmitted data, the basestation is aware that the downlink subframe with a DAI of 1 is the thirdone and thus receives receiving status feedback information from the UEin such a way that receiving status feedback information for the data of2 downlink subframes is transmitted in an uplink subframe. On the otherhand, when the UE receives the downlink subframe with a DAI of 1, the UEmay determine that the maximum value of the number of the downlinksubframes to which the base station transmits data is 2 and thus feedback receiving status feedback information in such a way that receivingstatus feedback information for the data of 2 downlink subframes istransmitted in an uplink subframe. However, when the UE does not receivethe PDCCH and data of the downlink subframe with a DAI of 1, althoughthe UE is not aware of the position of the downlink subframe with a DAIof 1, the UE discards the PDCCH and data of the downlink subframe with aDAI of 1 and may feed back fixed NACK or DRX, avoiding anyinconsistencies.

An exemplary implementation in which receiving status feedbackinformation is generated according to the position of the downlinksubframe with a DAI of 1 is described below. Again, assume M is equal to4 and 5 types of feedback information are generated with respect to eachCC.

When the downlink subframe with a DAI of 1 is the first one in the Mdownlink subframes, feedback information is transmitted in such a waythat receiving status feedback information for the data of 4 downlinksubframes is transmitted in an uplink subframe. Based on the sequencingof subframes for transmitting data in an order based on service type andDAI, the receiving status feedback information as fed back is 1) all ACKfor receiving status feedback information for the first 4 downlinksubframes, 2) all ACK for receiving status feedback information for thefirst 3 downlink subframes, 3) both ACK for receiving status feedbackinformation for the first 2 downlink subframes, 4) ACK for receivingstatus feedback information for the first downlink subframe, and 5) NACKor DRX for receiving status feedback information for the first downlinksubframe.

When the downlink subframe with a DAI of 1 is the second one in the Mdownlink subframes, feedback information is transmitted in such a waythat receiving status feedback information for the data of 3 downlinksubframes is transmitted in an uplink subframe. Based on the sequencingof subframes for transmitting data in an order based on service type andDAI, the receiving status feedback information is 1) all ACK forreceiving status feedback information for the first 3 downlinksubframes, 2) both ACK for receiving status feedback information for thefirst 2 downlink subframes, 3) ACK for receiving status feedbackinformation for the first downlink subframe, 4) NACK and ACKrespectively for receiving status feedback information for the first 2downlink subframes, 5) NACK for receiving status feedback informationfor the first downlink subframe and not ACK for receiving statusfeedback information for the second downlink subframe, if present, orDRX for receiving status feedback information for the first downlinksubframe.

When the downlink subframe with a DAI of 1 is the third one in the Mdownlink subframes, feedback information is transmitted in such a waythat receiving status feedback information for the data of 2 downlinksubframes is transmitted in an uplink subframe. Based on the sequencingof subframes for transmitting data in an order based on service type andDAI, the receiving status feedback information is 1) both ACK forreceiving status feedback information for the first 2 downlinksubframes, 2) ACK for receiving status feedback information for thefirst downlink subframe, 3) NACK and ACK respectively for receivingstatus feedback information for the first 2 downlink subframes, 4) NACKfor receiving status feedback information for the first downlinksubframe and not ACK for receiving status feedback information for thesecond downlink subframe, if present, and 5) DRX for receiving statusfeedback information for the first downlink subframe.

When the downlink subframe with a DAI of 1 is the fourth one in the Mdownlink subframes, feedback information is transmitted in such a waythat receiving status feedback information for the data of only 1downlink subframe is transmitted in an uplink subframe. In the case ofMIMO data transmission, complete receiving status feedback informationof the two Transport Blocks (TBs) may be fed back, i.e., two bits ofACK/NACK information and DRX status, 5 types of status in total. When noMIMO data transmission is applied, three types of feedback status, i.e.,ACK, NACK and DRX may be defined for a TB with two additional types ofnull status, i.e., 5 types of status in total. Alternatively, 5 types offeedback status may be mapped out in such a way that the receivingstatus feedback information of the other TB is a certain fixed value(ACK or NACK).

Another exemplary implementation in which feedback status is generatedaccording to the position of the downlink subframe with a DAI of 1 isdescribed below. Again, assume M is equal to 4 and 4 types of feedbackstatus are generated with respect to each CC.

When the downlink subframe with a DAI of 1 is the first one in the Mdownlink subframes, feedback information is transmitted in such a waythat receiving status feedback information for the data of 4 downlinksubframes is transmitted in an uplink subframe. Based on the sequencingof subframes for transmitting data in an order based on service type andDAI, the feedback status is fed back according to for example one of themethods as shown in FIGS. 6 through 11.

When the downlink subframe with a DAI of 1 is the second one in the Mdownlink subframes, feedback information is transmitted in such a waythat receiving status feedback information for the data of 3 downlinksubframes is transmitted in an uplink subframe. Based on the sequencingof subframes for transmitting data in an order based on service type andDAI, the feedback status is fed back according to, for example, themethod as shown in FIG. 5.

When the downlink subframe with a DAI of 1 is the third one in the Mdownlink subframes, feedback information is transmitted in such a waythat receiving status feedback information for the data of 2 downlinksubframes is transmitted in an uplink subframe. Based on the sequencingof subframes for transmitting data in an order based on service type andDAI, the feedback status is fed back according to, for example, themethod as shown in FIG. 4.

When the downlink subframe with a DAI of 1 is the fourth one in the Mdownlink subframes, feedback information is transmitted in such a waythat receiving status feedback information for the data of only 1downlink subframes is transmitted in an uplink subframe. In the case ofMIMO data transmission, complete receiving status feedback informationof the two TBs may be fed back, i.e., two bits of ACK/NACK information.When no MIMO data transmission is applied, three types of feedbackstatus, i.e., ACK, NACK and DRX may be defined for a TB with anadditional type of null status, i.e., 4 types of status in total.Alternatively, 4 types of feedback status may be mapped out in such away that the receiving status feedback information of the other TB is acertain fixed value (ACK or NACK).

Referring back to step 103 of FIG. 1, the receiving status feedbackinformation for the individual CCs may be joint-coded for transmission.For example, if the number of types of feedback status for each CC istaken as Y, the number of CCs is taken as N, and ceil (log₂ (Y)) bitsmay be used to represent the Y types of feedback status for each CC,where ceil ( ) represents rounding up, then the total number of bits tobe fed back is N·ceil (log₂ (Y)). Thereafter, the N·ceil (log₂ (Y)) bitsare channel-coded and transmitted. Alternatively, the total number oftypes of actual feedback status for the N CCs is Y^(N), and they can berepresented by ceil (N·log₂ (Y)) bits. The ceil (N·log₂(Y)) bits arethen channel-coded and transmitted. Here, the method for channel-codingmay be convolution coding, RM coding, and the like. In fact, when Y is apower of 2, the above two methods are equivalent to each other. Finally,the channel-coded bits may be transmitted, after being subject tosubsequent process, on ACK/NACK channels (for example, Physical UplinkControl Channel (PUCCH) format 2 or 3 channel, or others).

Still referring to step 103 of FIG. 1, the feedback status for theindividual CCs may be transmitted based on the channel selection method.Assume Y types of feedback status are fed back with respect to each CC.Here, in the definition of a mapping table based on channel selection,if a feedback status type denotes that feedback information for data ofthe first X downlink subframes that the UE receives is a combination ofACK and NACK, it can be ascertained that all the ACK/NACK channelscorresponding to the data for the first X downlink subframes exist. Ifdata of each downlink subframe correspond to at least one ACK/NACKchannel, which is configured semi-statically for an SPS service, or isobtained through a PDCCH for a dynamically scheduled service, thenACK/NACK information may be fed back on the X ACK/NACK channels based onchannel selection. In this way, a mapping table based on channelselection for a CA system is defined. More particularly, for eachcombination of feedback information for the individual CCs, an ACK/NACKchannel and a Quadrature Phase-Shift Keying (QPSK) constellation pointare selected for use from available ACK/NACK channels corresponding tothe combination of feedback information.

To reduce the complexity in the standardization, the 4-bit mapping tablefor Long Term Evolution-Advanced (LTE-A) Frequency Division Duplexing(FDD) may be multiplexed in LTE-A Time Division Duplexing (TDD). Assumethe total number of CCs is 2. In an FDD system, 2 bits of ACK/NACKinformation can be fed back with respect to each CC. In a TDD system,accordingly, two bits of ACK/NACK information also need to be fed backwith respect to each CC, i.e., the total number Y of feedback statustypes is equal to 4. In an FDD system, two ACK/NACK channels correspondto the two ACK/NACK bits for each CC. In a TDD system, accordingly, twoACK/NACK channels also need to be obtained for each CC.

More particularly, for the Primary CC (PCC), in absence of SPS service,the two ACK/NACK channels are obtained from the PDCCH for the downlinkdata with a DAI of 1. For example, assuming the minimum CCE index ofPDCCH is n, the two ACK/NACK channels may be obtained through mapping byusing an LTE method from CCE indexes n and n+1. Alternatively, the firstACK/NACK channel may be determined from the PDCCH for the downlink datawith a DAI of 1 and the second ACK/NACK channel may be determined fromthe PDCCH for the downlink data with a DAI of 2. In another alternative,the first ACK/NACK channel may be determined from the PDCCH for thedownlink data with a DAI of 1 and for the second ACK/NACK channel,multiple candidate channels may be configured by the higher layer andthe ACK/NACK Resource Indicator (ARI) for PDCCHs of the Secondary CC(SCC) may be scheduled to indicate an actually-used channel, therebyincreasing the flexibility in resource assignment. In the case of SPSservice, the ACK/NACK channels semi-statically configured for the SPSservice may be used for the channel selection. Here, two ACK/NACKchannels may be semi-statically assigned for the SPS service by thehigher layer, so that as with in absence of SPS service, two ACK/NACKchannels are available and no special processing is required.Alternatively, the higher layer configures, by using an LTE method, onlyone semi-static ACK/NACK channel, which serves as the first ACK/NACKchannel, and for the second ACK/NACK channel, multiple candidatechannels may be configured by the higher layer and the ARI for PDCCHs ofthe SCC may be scheduled to indicate an actually-used channel, therebyincreasing the flexibility in resource assignment. In anotheralternative, the higher layer configures, by using an LTE method, onlyone semi-static ACK/NACK channel, which serves as the first ACK/NACKchannel, and the ACK/NACK determined from the PDCCH for the downlinkdata with a DAI of 1 serves as the second ACK/NACK channel.

For the cross-CC scheduled SCC, in absence of SPS service, the twoACK/NACK channels are obtained from the PDCCH for the downlink data witha DAI of 1. For example, assuming the minimum CCE index of PDCCH is n,the two ACK/NACK channels may be obtained through mapping by using anLTE method from CCE indexes n and n+1. Alternatively, the first ACK/NACKchannel may be determined from the PDCCH for the downlink data with aDAI of 1 and the second ACK/NACK channel may be determined from thePDCCH for the downlink data with a DAI of 2. In another alternative, thefirst ACK/NACK channel may be determined from the PDCCH for the downlinkdata with a DAI of 1 and for the second ACK/NACK channel, multiplecandidate channels may be configured by the higher layer and the ARI forPDCCHs of the SCC may be scheduled to indicate an actually-used channel,thereby increasing the flexibility in resource assignment. For the SCCto which no cross-CC scheduling is applied, the two ACK/NACK channelsare configured by the higher layer and indicated by the ARIs. Moreparticularly, multiple candidate channels are configured by the higherlayer and the ARIs for PDCCHs of the SCC are scheduled to indicate twoactually-used channels, thereby increasing the flexibility in resourceassignment.

After the ACK/NACK channels are assigned according to the above methods,the two ACK/NACK channels for the PCC are denoted as channel 1 andchannel 2, and the two ACK/NACK channels for the SCC are denoted aschannel 3 and channel 4. Next, a correspondence between the 4 types offeedback status for each CC and the two-bit ACK/NACK information typesfor each CC is further defined in a mapping table for FDD. For example,a mapping relationship as shown in FIG. 7 may be employed. In this way,the 4-bit mapping table for FDD may be multiplexed in a TDD system withthe above channel selection method and mapping relationship.

FIG. 3 illustrates a 4-bit mapping table employed in an LTE-A FDD systemaccording to an exemplary embodiment of the present invention.

Referring to FIG. 3, feedback status types may be defined for differentvalues of M with one of the methods as illustrated in FIGS. 4, 5 and 6,and the mapping relationship between feedback status types and two-bitACK/NACK information types for each CC in a mapping table for FDD may beemployed as shown in FIG. 7.

FIG. 7 illustrates a mapping relationship from feedback status to 2-bitACK/NACK in an FDD table according to an exemplary embodiment of thepresent invention.

Referring to FIG. 7, a feedback status type 4) needs to be mapped to 2bits (N, N), because they both indicate feedback information NACK orDRX, feedback status type 3) is mapped to 2 bits (A, N), which isdetermined from the 4-bit mapping table as shown in FIG. 3. In a TDDsystem, when the UE receives only one piece of SPS data from the PCC,the UE actually has only one available ACK/NACK channel semi-staticallyconfigured for the SPS service. To indicate the ACK/NACK feedbackinformation in this case, the selected ACK/NACK channel is either thisACK/NACK channel semi-statically configured for the SPS service or anACK/NACK channel of the SCC. Referring back to FIG. 3, the aboverequirements are met only when the feedback information for the PCC is(A, N), i.e., the selected ACK/NACK channel is either the first ACK/NACKchannel of the PCC or a corresponding ACK/NACK channel of the SCC. Next,the ACK/NACK channels are assigned according to one of the methodsdescribed above. Still referring to FIG. 3, when the 2 bits for the SCCrepresent any of the combinations (A, N), (N, A) and (A, A), twocandidate channels of the SCC need to be configured to support thechannel selection. Whereas the UE may receive only data of one downlinksubframe with a DAI of 1 from the SCC, or the base station may actuallytransmit only data of one downlink subframe with a DAI of 1 through theSCC. Therefore, it is not practical to determine an ACK/NACK channel forthe data of the downlink subframe with a DAI of 1 and determine anotherACK/NACK channel for the data of the downlink subframe with a DAI of 2.In contrast, the ACK/NACK channels may not suffice for the channelselection. In conclusion, after the mapping of feedback status isdetermined and the ACK/NACK channels to be used are assigned, the firstand the second ACK/NACK channels for the PCC are denoted as channel 1and channel 2, respectively, and the first and the second ACK/NACKchannels for the SCC are denoted as channel 3 and channel 4,respectively, thereby fully multiplexing the 4-bit mapping table for FDDas shown in FIG. 3.

In a 4-bit table for FDD, when feedback status types for Pcell and Scellare both (N, N) or DRX, it can be identified that the feedback statustype for Pcell is which of (N, N) and DRX. Accordingly, in a TDD system,when feedback status types for Pcell and Scell are both feedback statustype 4), there may be two different instances of feedback status type 4)for Pcell. In the first instance, no SPS service is applied and the UEcan determine from the DAI that the PDCCH with a DAI of 1 has been lost,where the UE may not have an available ACK/NACK channel at all. Thesecond instance refers to feedback information in an instance other thanthe first instance of feedback status type 4). In the second instance,more particularly, an SPS service is configured where the UE has atleast one available ACK/NACK channel, or in absence of SPS data, the UEhas received dynamic data scheduled with respect to at least the PDCCHwith a DAI of 1, where the UE also has at least one available ACK/NACKchannel. In this way, corresponding to (N, N, N, N) and (N, N, D, D) inthe table as shown in FIG. 3, the channel and constellation pointindicate the second instance of feedback status type 4) for Pcell andfeedback status type 4) for Scell. In regard to (D, D, N, N) and (D, D,D, D) in the table as shown in FIG. 3, the UE may not transmit anyuplink signal, which indicates the first instance of feedback statustype 4) for Pcell and feedback status type 4) for Scell.

The above exemplary implementation has been described with reference toFIG. 3. Hereinafter, exemplary implementations will be described withreference to a 4-bit mapping table supporting the independent existenceof 4 ACK/NACK channels, for example, the mapping table as shown in FIG.12.

FIG. 12 illustrates a 4-bit mapping table according to an exemplaryembodiment of the present invention.

Referring to FIG. 12, the methods as illustrated in FIGS. 4, 5 and 6 mayalso be employed to define feedback status types for different values ofM, and to define a mapping relationship between feedback status typesand two-bit ACK/NACK information types, the table as shown in FIG. 7 mayneed to be extended, i.e., interpreting the feedback information N inFIG. 3 as NACK or DRX, so as to obtain a mapping table as shown in FIG.13. Here, there may be two different instances of feedback status type4) in FIG. 13. In the first instance, no SPS service is applied and theUE can determine from the DAI that the PDCCH with a DAI of 1 has beenlost, where the UE may not have an available ACK/NACK channel at all,corresponding to the feedback information (D, N/D) in the mapping table,as shown in FIG. 12. The second instance refers to feedback informationin an instance other than the first instance of feedback status type 4).In the second instance, more particularly, an SPS service is configuredwhere the UE has at least one available ACK/NACK channel, or in absenceof SPS data, the UE has received dynamic data scheduled with respect toat least the PDCCH with a DAI of 1, where the UE also has at least oneavailable ACK/NACK channel. In this way, after performing a mappingbetween feedback status types and 2-bit ACK/NACK information typesaccording to FIG. 13, ACK/NACK information may be fed back using thechannel selection method according to the 4-bit mapping table as shownin FIG. 12.

FIG. 13 illustrates a mapping relationship from feedback status to 2-bitACK/NACK according to an exemplary embodiment of the present invention.

Referring to FIG. 13, feedback status type 4) needs to be mapped to 2bits (N/D, N/D), because they both indicate that the feedbackinformation is NACK or DRX. In the mapping table as shown in FIG. 12,when feedback status types of Pcell and Scell are feedback status type4), it can be identified that the feedback status type of Pcell is oneof the two instances of feedback status type 4). When the feedbackstatus type of Pcell is the second instance of feedback status type 4),a QPSK constellation point of the ACK/NACK channel that is present isused for uplink transmission. In the mapping table as shown in FIG. 12,this ACK/NACK channel corresponds to h0. In FIG. 13, feedback statustype 3) is mapped to 2 bits (A, N/D). Feedback status type 3) indicatesthat with respect to one CC, the UE may receive only data of onesubframe and thus has only one available ACK/NACK channel. For the PCC,for example, when the UE receives only one piece of SPS data from thePCC, only one ACK/NACK channel semi-statically configured for the SPSservice is available. To transmit an uplink feedback signal in thiscase, the UE selects either this ACK/NACK channel semi-staticallyconfigured for the SPS service or an ACK/NACK channel of the SCC as anACK/NACK channel. According to the above analyses of feedback statustype 4), this ACK/NACK channel corresponds to h0 in the mapping table asshown in FIG. 12, and h1 does not exist. Referring back to FIG. 12, whenthe feedback information for the PCC is (A, N/D), the selected channelis either h0 or a channel of the SCC (h2 or H3), and h1 is impossible.Therefore, feedback status type 3) needs to be mapped to the 2 bits (A,N/D). Feedback status types 1 and 2) indicate that with respect to oneCC, the UE receives data of at least two subframes and thus has at leasttwo available ACK/NACK channels. Therefore, the two pieces of mappedACK/NACK information may not need to be limited. In FIG. 13, feedbackstatus type 1) is mapped to (A, A) and feedback status type 2) is mappedto (N/D, A). In conclusion, after the mapping of feedback status isdetermined and the ACK/NACK channels to be used are assigned, the firstand the second ACK/NACK channels for the PCC are denoted as channel 1and channel 2, respectively, and the first and the second ACK/NACKchannels for the SCC are denoted as channel 3 and channel 4,respectively, thereby fully multiplexing the 4-bit mapping table for FDDas shown in FIG. 12.

Furthermore, the channel selection method supporting CA for LTE-A TDDmay further support a backing operation. More particularly, when the UEonly receives data of the PCC, the method may be backed to ACK/NACKmultiplexing in LTE, where the number of downlink subframes in thebundling window is denoted as M, a piece of ACK/NACK information isobtained for each downlink subframe, an ACK/NACK channel is assignedimplicitly to each downlink subframe in the bundling window, i.e., Mchannels are obtained implicitly, and the channel selection method isused to feed back the M pieces of ACK/NACK information. The channelselection mapping table as used herein may be a table defined in LTE,the table as shown in FIG. 12, or others. According to the LTE method,the available ACK/NACK channels are obtained implicitly from the minimumCCE index of PDCCH for each subframe in the bundling window. When the UEreceives data of a subframe from at least one SCC, the channel selectionmethod supporting CA is employed. The ACK/NACK channel assignment forthe SCC may also employ the channel selection method described above.With respect to the ACK/NACK channel assignment for the PCC, oneACK/NACK channel for each subframe in the bundling window has alreadybeen used upon the backing operation. That is, one ACK/NACK channelsemi-statically configured by the higher layer has been used for asubframe transmitting SPS data, or the ACK/NACK channel mappedimplicitly from the minimum CCE index of the PDCCH has been used fordynamic data. In this way, upon assignment of ACK/NACK channel for thePCC in absence of the SPS service, the first ACK/NACK channel may bedetermined from the PDCCH for downlink data with a DAI of 1.

However, the ACK/NACK channel mapped from the minimum CCE index of thePDCCH cannot be used, and the second ACK/NACK channel may be determinedfrom the PDCCH for downlink data with a DAI of 2, but the ACK/NACKchannel mapped from the minimum CCE index of the PDCCH cannot be used.Alternatively, the first ACK/NACK channel may be determined from thePDCCH for downlink data with a DAI of 1, but the ACK/NACK channel mappedfrom the minimum CCE index of the PDCCH cannot be used. For the secondACK/NACK channel, multiple candidate channels may be configured by thehigher layer and the ARI for PDCCHs of the SCC may be scheduled toindicate an actually-used channel, thereby increasing the flexibility inresource assignment. In another alternative, the two ACK/NACK channelsare configured by the higher layer and indicated by ARIs. Moreparticularly, multiple candidate channels are configured by the higherlayer and the ARI for PDCCHs of the SCC may be scheduled to indicate anactually-used channel, thereby increasing the flexibility in resourceassignment. Upon assignment of ACK/NACK channel for the PCC in the caseof the SPS service, the two ACK/NACK channels may be configured by thehigher layer and indicated by ARIs. More particularly, multiplecandidate channels are configured by the higher layer and the ARI forPDCCHs of the SCC may be scheduled to indicate an actually-used channel,thereby increasing the flexibility in resource assignment.Alternatively, the first ACK/NACK channel is configured by the higherlayer and indicated by an ARI. More particularly, multiple candidatechannels are configured by the higher layer and the ARI for PDCCHs ofthe SCC is scheduled to indicate an actually-used channel, therebyincreasing the flexibility in resource assignment, and the secondACK/NACK channel may be determined from the PDCCH for downlink data witha DAI of 1. However, the ACK/NACK channel mapped from the minimum CCEindex of the PDCCH cannot be used.

FIG. 14 is a block diagram illustrating an apparatus for feeding backdata receiving status according to an exemplary embodiment of thepresent invention.

Referring to FIG. 14, a User Equipment (UE) includes a duplexer 1400, areception modem 1402, a message processor 1404, a controller 1406, aHARQ controller 1408, a message generator 1410, and a transmission modem1412.

The duplexer 1400 transmits a transmit signal provided from thetransmission modem 1412 through an antenna according to a duplexingscheme, and provides a receive signal from the antenna to the receptionmodem 1402.

The reception modem 1402 converts and demodulates a Radio Frequency (RF)signal provided from the duplexer 1400 into a baseband signal. Thereception modem 1402 may include an RF processing block, a demodulationblock, a channel decoding block, and the like. The RF processing blockconverts an RF signal provided from the duplexer 1400 into a basebandsignal according to the control of the controller 1406. The demodulationblock may include a Fast Fourier Transform (FFT) operator, and the like,for extracting data loaded on each subcarrier from a signal providedfrom the RF processing block. The channel decoding block may include ademodulator, a de-interleaver, a channel decoder, and the like.

The message processor 1404 extracts control information from a signalprovided from the reception modem 1402 and provides the controlinformation to the controller 1406 which controls an operation of theUE.

The controller 1406 controls to feedback ACK/NACK with respect toreceived downlink data to the Base Station (BS). The controller 1406controls to transmit receiving status feedback information with respectto the received downlink data to the BS according to the HARQ controller1408.

The HARQ controller 1408 sequences downlink subframes for transmittingdata for the UE with respect to each CC. The HARQ controller 1408generates receiving status feedback information for the first X downlinksubframes with respect to each CC according to the order of the downlinksubframes, where X M, M being the number of downlink subframes on a CC.The HARQ controller 1408 controls to transmit the receiving statusfeedback information generated with respect to each CC to the basestation. Additionally, the HARQ controller 1408 may first performspatial bundling on the receiving status feedback information for twoCode Words (CWs) in each downlink subframe. That is, the HARQ controller1408 performs operation needed for transmitting the receiving statusfeedback information to the BS as described above with reference toFIGS. 1 through 13.

The message generator 1410 generates a control message to be ACK/NACKfeedback according to the control of the controller 1406.

The transmission modem 1412 encodes and converts data to be transmittedto an MS and a control message provided from the message generator 1408,into an RF signal, and transmits the RF signal to the duplexer 1400. Thetransmission modem 1412 may include a channel encoding block, amodulation block, an RF processing block, and the like. The channelencoding block may include a modulator, an interleaver, a channelencoder, and the like. The modulation block may include an Inverse FastFourier Transform (IFFT) operator, and the like, for mapping a signalprovided from the channel encoding block to each subcarrier. The RFprocessing block converts a baseband signal provided from the modulationblock into an RF signal, and outputs the RF signal to the duplexer 1400.

As can be seen from the above description, exemplary embodiments of thepresent invention have the following advantages.

The UE sequences downlink subframes for transmitting data with respectto each CC, generates receiving status feedback information for thefirst X downlink subframes according to the result of the sequencing,and transmits the receiving status feedback information for each CC tothe base station. Because the UE reports the receiving status for only Xdownlink subframes, the base station may perform a HARQ processing onthe first X downlink subframes. For the last downlink subframes, thebase station may perform a process by assuming that the UE does notreceive the PDCCHs. Therefore, the base station can reach an agreementwith the UE on the receiving status of the UE, ensuring that the UE willnot misinterpret the receiving status for the downlink subframes due toinconsistencies with the base station between transmitting and receivingfeedback so that the HARQ transmission is affected. Moreover, anexemplary embodiment of the present invention saves the uplink overheadsoccupied by the receiving status feedback information and increases theuplink coverage area, by reducing the number of receiving statusfeedback information pieces.

Furthermore, the form of receiving status feedback information may bechanged flexibly according to the position of the downlink subframe witha DAI of 1 in the M downlink subframes, thereby increasing, to thegreatest extent, the information amount of receiving status feedbackinformation for each CC without increasing the overheads.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method for feeding back data receiving status,applied to a system, the method comprising: sequencing, by a UserEquipment (UE), downlink subframes for transmitting data with respect toeach Component Carrier (CC); generating receiving status feedbackinformation for the first X downlink subframes with respect to each CCaccording to the result of the sequencing, where X≧M, wherein M is thenumber of downlink subframes on each CC; and transmitting the receivingstatus feedback information generated with respect to each CC to a basestation.
 2. The method according to claim 1, wherein the sequencing ofthe downlink subframes for transmitting data comprises, sequencing bysequencing priorities set from higher to lower for downlink subframestransmitting Semi Persistent Scheduling (SPS) service data and downlinksubframes transmitting dynamic data, wherein downlink subframestransmitting SPS service data are sequenced by subframe indexes anddownlink subframes transmitting dynamic data are sequenced in anascending order of Downlink Assignment Indexes (DAIs).
 3. The methodaccording to claim 1, wherein the receiving status feedback informationcomprises at least one of: all Acknowledgement (ACK) for receivingstatus feedback information for the first X downlink subframes; allNon-Acknowledgement (NACK) for receiving status feedback information forthe first X downlink subframes; ACK for receiving status feedbackinformation for some of the first X downlink subframes; NACK forreceiving status feedback information for some of the first X downlinksubframes; and Discontinuous Reception (DRX) for receiving statusfeedback information for some of the first X downlink subframes.
 4. Themethod according to claim 1, wherein in the generating of the receivingstatus feedback information, spatial bundling of at least one ofreceiving status feedback information for two Code Words (CWs) in eachdownlink subframe in the first X downlink subframes and receiving statusfeedback information is generated respectively for the two CWs in eachsubframe of the first X downlink subframes.
 5. The method according toclaim 1, wherein the CCs comprise at least one of all the downlink CCsin a cell, downlink CCs configured for the UE, and active CCs configuredfor the UE, further comprises generating, by the UE, DiscontinuousReception (DRX) for receiving status feedback information with respectto a CC from which no data is received.
 6. The method according to claim1, wherein the generating of the receiving status feedback informationfurther comprises: determining, by the UE, a form of receiving statusfeedback information according to a position of a downlink subframe witha Downlink Assignment Index (DAI) of 1 in the M downlink subframes; andperforming the generating of receiving status feedback information forthe first X downlink subframes according to the determined form, whereinthe determining of the form of the receiving status feedback informationcomprises: determining, by the UE, a maximum number N of downlinksubframes to which the base station transmits downlink data, accordingto the position of the downlink subframe with a DAI of 1 in the Mdownlink subframes; and determining a form of receiving status feedbackinformation corresponding to a value of N.
 7. The method according toclaim 1, wherein the transmitting of the receiving status feedbackinformation further comprises implementing, by the UE, the transmissionbased on a channel selection method with respect to feedback status foreach CC; and wherein the channel selection method comprises at least oneof: obtaining two Acknowledgement/Non-Acknowledgement (ACK/NACK)channels from a Physical Downlink Control Channel (PDCCH) for downlinkdata with a DAI of 1; determining a first ACK/NACK channel from a PDCCHfor downlink data with a DAI of 1 and determining a second ACK/NACKchannel from a PDCCH for downlink data with a DAI of 2; determining afirst ACK/NACK channel from a PDCCH for downlink data with a DAI of 1,configuring multiple candidate channels by a higher layer, andscheduling an ACK/NACK Resource Indicator (ARI) for PDCCHs to indicate asecond ACK/NACK channel; and configuring multiple candidate channels bya higher layer and scheduling ARIs for PDCCHs to indicate twoactually-used channels.
 8. The method according to claim 7, wherein thechannel selection method comprises at least one of: semi-staticallyassigning, in a case of Semi Persistent Scheduling (SPS) service, twoAcknowledgement/Non-Acknowledgement (ACK/NACK) channels for the SPSservice by a higher layer; configuring a semi-statically ACK/NACKchannel to serve as a first ACK/NACK channel, and for the secondACK/NACK channel, configuring multiple candidate channels by a higherlayer, and scheduling an ACK/NACK Resource Indicator (ARI) for PDCCHs ofSecondary CC (SCC) to indicate an actually-used channel; and configuringa semi-statically ACK/NACK channel to serve as a first ACK/NACK channeland determining an ACK/NACK from a PDCCH for downlink data with a DAI of1 serving as a second ACK/NACK channel.
 9. The method according to claim7, wherein, according to the channel selection method, a correspondencerelationship is defined between 4 feedback status types for each CC andtwo-bit ACK/NACK information types using a 4-bit mapping table, whereinthe fourth feedback status type includes a first instance referring toan instance in which no Semi Persistent Scheduling (SPS) service isapplied and the UE can determine from the DAI that a PDCCH with a DAI of1 has been lost, and a second instance referring to feedback informationin an instance other than the first instance of the fourth feedbackstatus type.
 10. The method according to claim 7, wherein, when the UEonly receives data of a Primary CC (PCC), the channel selection methodcomprises an LTE channel selection method; and when the UE receives dataof a subframe from at least one Secondary CC (SCC), the channelselection method comprises a channel selection method supporting CarrierAggregation (CA).
 11. An apparatus for feeding back data receivingstatus, applied to a Long Term Evolution-Advanced (LTE-A) system, theapparatus comprising: a User Equipment (UE) for sequencing downlinksubframes for transmitting data with respect to each Component Carrier(CC), for generating receiving status feedback information for the firstX downlink subframes with respect to each CC according to the result ofthe sequencing, where X≦M, wherein M is the number of downlink subframeson each CC, and for transmitting the receiving status feedbackinformation generated with respect to each CC to a base station.
 12. Theapparatus according to claim 11, wherein the UE performs sequencing bysetting sequencing priorities from higher to lower for downlinksubframes transmitting Semi Persistent Scheduling (SPS) service data anddownlink subframes transmitting dynamic data, wherein downlink subframestransmitting SPS service data are sequenced by subframe indexes anddownlink subframes transmitting dynamic data are sequenced in anascending order of Downlink Assignment Indexes (DAIs).
 13. The apparatusaccording to claim 11, wherein the receiving status feedback informationcomprises at least one of: all Acknowledgement (ACK) for receivingstatus feedback information for the first X downlink subframes; allNon-Acknowledgement (NACK) for receiving status feedback information forthe first X downlink subframes; ACK for receiving status feedbackinformation for some of the first X downlink subframes; NACK forreceiving status feedback information for some of the first X downlinksubframes; and Discontinuous Reception (DRX) for receiving statusfeedback information for some of the first X downlink subframes.
 14. Theapparatus according to claim 11, wherein, in the generating of thereceiving status feedback information, the UE generates spatial bundlingof at least one of receiving status feedback information for two CodeWords (CWs) in each downlink subframe in the first X downlink subframesand receiving status feedback information, respectively, for the two CWsin each subframe of the first X downlink subframes.
 15. The apparatusaccording to claim 11, wherein each of the CCs comprises at least one ofall the downlink CCs in a cell, downlink CCs configured for the UE, andactive CCs configured for the UE, wherein the UE generates DiscontinuousReception (DRX) for receiving status feedback information with respectto a CC from which no data is received.
 16. The apparatus according toclaim 11, wherein the UE determines a form of receiving status feedbackinformation according to a position of a downlink subframe with aDownlink Assignment Index (DAI) of 1 in the M downlink subframes; andperforms the generating of receiving status feedback information for thefirst X downlink subframes according to the determined form, and whereinthe UE determines a maximum number N of downlink subframes to which thebase station transmits downlink data, according to the position of thedownlink subframe with a DAI of 1 in the M downlink subframes; anddetermines a form of receiving status feedback information correspondingto a value of N.
 17. The apparatus according to claim 11, wherein the UEimplements the transmission based on a channel selection scheme withrespect to feedback status for each CC; and wherein, in implementing thetransmission based on the channel selection scheme, the UE performs atleast one of: obtains two Acknowledgement/Non-Acknowledgement (ACK/NACK)channels from a Physical Downlink Control Channel (PDCCH) for downlinkdata with a DAI of 1; determines a first ACK/NACK channel from a PDCCHfor downlink data with a DAI of 1 and determines a second ACK/NACKchannel from a PDCCH for downlink data with a DAI of 2; determines afirst ACK/NACK channel from a PDCCH for downlink data with a DAI of 1,configures multiple candidate channels by a higher layer, and schedulesan ACK/NACK Resource Indicator (ARI) for PDCCHs to indicate a secondACK/NACK channel; and configures multiple candidate channels by a higherlayer and schedules ARIs for PDCCHs to indicate two actually-usedchannels.
 18. The apparatus according to claim 17, wherein, inimplementing the transmission based on the channel selection scheme, theUE performs at least one of: semi-statically assigns, in a case of SemiPersistent Scheduling (SPS) service, twoAcknowledgement/Non-Acknowledgement (ACK/NACK) channels for the SPSservice by a higher layer; configures a semi-statically ACK/NACK channelto serve as a first ACK/NACK channel, and for the second ACK/NACKchannel, configures multiple candidate channels by a higher layer, andschedules an ACK/NACK Resource Indicator (ARI) for PDCCHs of SecondaryCC (SCC) to indicate an actually-used channel; and configures asemi-statically ACK/NACK channel to serve as a first ACK/NACK channeland determines an ACK/NACK from a PDCCH for downlink data with a DAI of1 serving as a second ACK/NACK channel.
 19. The apparatus according toclaim 17, wherein, when the UE implements the transmission based on thechannel selection scheme, a correspondence relationship is definedbetween 4 feedback status types for each CC and two-bit ACK/NACKinformation types using a 4-bit mapping table, wherein the fourthfeedback status type includes a first instance referring to an instancein which no Semi Persistent Scheduling (SPS) service is applied and theUE can determine from the DAI that a PDCCH with a DAI of 1 has beenlost, and a second instance referring to feedback information in aninstance other than the first instance of the fourth feedback statustype.
 20. The apparatus according to claim 17, wherein, when the UE onlyreceives data of a Primary CC (PCC), the channel selection schemecomprises an LTE channel selection scheme; and when the UE receives dataof a subframe from at least one Secondary CC (SCC), the channelselection scheme comprises a channel selection scheme supporting CarrierAggregation (CA).